// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Linux I2C core
 *
 * Copyright (C) 1995-99 Simon G. Vogl
 *   With some changes from Kyösti Mälkki <kmalkki@cc.hut.fi>
 *   Mux support by Rodolfo Giometti <giometti@enneenne.com> and
 *   Michael Lawnick <michael.lawnick.ext@nsn.com>
 *
 * Copyright (C) 2013-2017 Wolfram Sang <wsa@kernel.org>
 */

#define pr_fmt(fmt) "i2c-core: " fmt

#include <dt-bindings/i2c/i2c.h>
#include <linux/acpi.h>
#include <linux/clk/clk-conf.h>
#include <linux/completion.h>
#include <linux/delay.h>
#include <linux/err.h>
#include <linux/errno.h>
#include <linux/gpio/consumer.h>
#include <linux/i2c.h>
#include <linux/i2c-smbus.h>
#include <linux/idr.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/irqflags.h>
#include <linux/jump_label.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/of_device.h>
#include <linux/of.h>
#include <linux/of_irq.h>
#include <linux/pinctrl/consumer.h>
#include <linux/pm_domain.h>
#include <linux/pm_runtime.h>
#include <linux/pm_wakeirq.h>
#include <linux/property.h>
#include <linux/rwsem.h>
#include <linux/slab.h>

#include "i2c-core.h"

#define CREATE_TRACE_POINTS
#include <trace/events/i2c.h>

#define I2C_ADDR_OFFSET_TEN_BIT 0xa000
#define I2C_ADDR_OFFSET_SLAVE 0x1000

#define I2C_ADDR_7BITS_MAX 0x77
#define I2C_ADDR_7BITS_COUNT (I2C_ADDR_7BITS_MAX + 1)

#define I2C_ADDR_DEVICE_ID 0x7c

/*
 * core_lock protects i2c_adapter_idr, and guarantees that device detection,
 * deletion of detected devices are serialized
 */
static DEFINE_MUTEX(core_lock);
static DEFINE_IDR(i2c_adapter_idr);

static int i2c_check_addr_ex(struct i2c_adapter *adapter, int addr);
static int i2c_detect(struct i2c_adapter *adapter, struct i2c_driver *driver);

static DEFINE_STATIC_KEY_FALSE(i2c_trace_msg_key);
static bool is_registered;

int i2c_transfer_trace_reg(void)
{
    static_branch_inc(&i2c_trace_msg_key);
    return 0;
}

void i2c_transfer_trace_unreg(void)
{
    static_branch_dec(&i2c_trace_msg_key);
}

const struct i2c_device_id *i2c_match_id(const struct i2c_device_id *id, const struct i2c_client *client)
{
    if (!(id && client)) {
        return NULL;
    }

    while (id->name[0]) {
        if (strcmp(client->name, id->name) == 0) {
            return id;
        }
        id++;
    }
    return NULL;
}
EXPORT_SYMBOL_GPL(i2c_match_id);

static int i2c_device_match(struct device *dev, struct device_driver *drv)
{
    struct i2c_client *client = i2c_verify_client(dev);
    struct i2c_driver *driver;
    /* Attempt an OF style match */
    if (i2c_of_match_device(drv->of_match_table, client)) {
        return 1;
    }
    /* Then ACPI style match */
    if (acpi_driver_match_device(dev, drv)) {
        return 1;
    }
    driver = to_i2c_driver(drv);
    /* Finally an I2C match */
    if (i2c_match_id(driver->id_table, client)) {
        return 1;
    }
    return 0;
}

static int i2c_device_uevent(struct device *dev, struct kobj_uevent_env *env)
{
    struct i2c_client *client = to_i2c_client(dev);
    int rc;

    rc = of_device_uevent_modalias(dev, env);
    if (rc != -ENODEV) {
        return rc;
    }

    rc = acpi_device_uevent_modalias(dev, env);
    if (rc != -ENODEV) {
        return rc;
    }

    return add_uevent_var(env, "MODALIAS=%s%s", I2C_MODULE_PREFIX, client->name);
}

/* i2c bus recovery routines */
static int get_scl_gpio_value(struct i2c_adapter *adap)
{
    return gpiod_get_value_cansleep(adap->bus_recovery_info->scl_gpiod);
}

static void set_scl_gpio_value(struct i2c_adapter *adap, int val)
{
    gpiod_set_value_cansleep(adap->bus_recovery_info->scl_gpiod, val);
}

static int get_sda_gpio_value(struct i2c_adapter *adap)
{
    return gpiod_get_value_cansleep(adap->bus_recovery_info->sda_gpiod);
}

static void set_sda_gpio_value(struct i2c_adapter *adap, int val)
{
    gpiod_set_value_cansleep(adap->bus_recovery_info->sda_gpiod, val);
}

static int i2c_generic_bus_free(struct i2c_adapter *adap)
{
    struct i2c_bus_recovery_info *bri = adap->bus_recovery_info;
    int ret = -EOPNOTSUPP;

    if (bri->get_bus_free) {
        ret = bri->get_bus_free(adap);
    } else if (bri->get_sda) {
        ret = bri->get_sda(adap);
    }

    if (ret < 0) {
        return ret;
    }

    return ret ? 0 : -EBUSY;
}

/*
 * We are generating clock pulses. ndelay() determines durating of clk pulses.
 * We will generate clock with rate 100 KHz and so duration of both clock levels
 * is: delay in ns = (10^6 / 100) / 2
 */
#define RECOVERY_NDELAY 5000
#define RECOVERY_NDELAY_HALF 2
#define RECOVERY_CLK_CNT 9
#define RECOVERY_CLK_CNT_TWICE 2

int i2c_generic_scl_recovery(struct i2c_adapter *adap)
{
    struct i2c_bus_recovery_info *bri = adap->bus_recovery_info;
    int i = 0, scl = 1, ret = 0;

    if (bri->prepare_recovery) {
        bri->prepare_recovery(adap);
    }
    if (bri->pinctrl) {
        pinctrl_select_state(bri->pinctrl, bri->pins_gpio);
    }

    /*
     * If we can set SDA, we will always create a STOP to ensure additional
     * pulses will do no harm. This is achieved by letting SDA follow SCL
     * half a cycle later. Check the 'incomplete_write_byte' fault injector
     * for details. Note that we must honour tsu:sto, 4us, but lets use 5us
     * here for simplicity.
     */
    bri->set_scl(adap, scl);
    ndelay(RECOVERY_NDELAY);
    if (bri->set_sda) {
        bri->set_sda(adap, scl);
    }
    ndelay(RECOVERY_NDELAY / RECOVERY_NDELAY_HALF);

    /*
     * By this time SCL is high, as we need to give 9 falling-rising edges
     */
    while (i++ < RECOVERY_CLK_CNT * RECOVERY_CLK_CNT_TWICE) {
        if (scl) {
            /* SCL shouldn't be low here */
            if (!bri->get_scl(adap)) {
                dev_err(&adap->dev, "SCL is stuck low, exit recovery\n");
                ret = -EBUSY;
                break;
            }
        }

        scl = !scl;
        bri->set_scl(adap, scl);
        /* Creating STOP again, see above */
        if (scl) {
            /* Honour minimum tsu:sto */
            ndelay(RECOVERY_NDELAY);
        } else {
            /* Honour minimum tf and thd:dat */
            ndelay(RECOVERY_NDELAY / RECOVERY_NDELAY_HALF);
        }
        if (bri->set_sda) {
            bri->set_sda(adap, scl);
        }
        ndelay(RECOVERY_NDELAY / RECOVERY_NDELAY_HALF);

        if (scl) {
            ret = i2c_generic_bus_free(adap);
            if (ret == 0) {
                break;
            }
        }
    }

    /* If we can't check bus status, assume recovery worked */
    if (ret == -EOPNOTSUPP) {
        ret = 0;
    }

    if (bri->unprepare_recovery) {
        bri->unprepare_recovery(adap);
    }
    if (bri->pinctrl) {
        pinctrl_select_state(bri->pinctrl, bri->pins_default);
    }

    return ret;
}
EXPORT_SYMBOL_GPL(i2c_generic_scl_recovery);

int i2c_recover_bus(struct i2c_adapter *adap)
{
    if (!adap->bus_recovery_info) {
        return -EOPNOTSUPP;
    }

    dev_dbg(&adap->dev, "Trying i2c bus recovery\n");
    return adap->bus_recovery_info->recover_bus(adap);
}
EXPORT_SYMBOL_GPL(i2c_recover_bus);

static void i2c_gpio_init_pinctrl_recovery(struct i2c_adapter *adap)
{
    struct i2c_bus_recovery_info *bri = adap->bus_recovery_info;
    struct device *dev = &adap->dev;
    struct pinctrl *p = bri->pinctrl;

    /*
     * we can't change states without pinctrl, so remove the states if
     * populated
     */
    if (!p) {
        bri->pins_default = NULL;
        bri->pins_gpio = NULL;
        return;
    }

    if (!bri->pins_default) {
        bri->pins_default = pinctrl_lookup_state(p, PINCTRL_STATE_DEFAULT);
        if (IS_ERR(bri->pins_default)) {
            dev_dbg(dev, PINCTRL_STATE_DEFAULT " state not found for GPIO recovery\n");
            bri->pins_default = NULL;
        }
    }
    if (!bri->pins_gpio) {
        bri->pins_gpio = pinctrl_lookup_state(p, "gpio");
        if (IS_ERR(bri->pins_gpio)) {
            bri->pins_gpio = pinctrl_lookup_state(p, "recovery");
        }

        if (IS_ERR(bri->pins_gpio)) {
            dev_dbg(dev, "no gpio or recovery state found for GPIO recovery\n");
            bri->pins_gpio = NULL;
        }
    }

    /* for pinctrl state changes, we need all the information */
    if (bri->pins_default && bri->pins_gpio) {
        dev_info(dev, "using pinctrl states for GPIO recovery");
    } else {
        bri->pinctrl = NULL;
        bri->pins_default = NULL;
        bri->pins_gpio = NULL;
    }
}

#define I2C_US_DELAY_COUNT_TEN 10

static int i2c_gpio_init_generic_recovery(struct i2c_adapter *adap)
{
    struct i2c_bus_recovery_info *bri = adap->bus_recovery_info;
    struct device *dev = &adap->dev;
    struct gpio_desc *gpiod;
    int ret = 0;

    /*
     * don't touch the recovery information if the driver is not using
     * generic SCL recovery
     */
    if (bri->recover_bus && bri->recover_bus != i2c_generic_scl_recovery) {
        return 0;
    }

    /*
     * pins might be taken as GPIO, so we should inform pinctrl about
     * this and move the state to GPIO
     */
    if (bri->pinctrl) {
        pinctrl_select_state(bri->pinctrl, bri->pins_gpio);
    }

    /*
     * if there is incomplete or no recovery information, see if generic
     * GPIO recovery is available
     */
    if (!bri->scl_gpiod) {
        gpiod = devm_gpiod_get(dev, "scl", GPIOD_OUT_HIGH_OPEN_DRAIN);
        if (PTR_ERR(gpiod) == -EPROBE_DEFER) {
            ret = -EPROBE_DEFER;
            goto cleanup_pinctrl_state;
        }
        if (!IS_ERR(gpiod)) {
            bri->scl_gpiod = gpiod;
            bri->recover_bus = i2c_generic_scl_recovery;
            dev_info(dev, "using generic GPIOs for recovery\n");
        }
    }

    /* SDA GPIOD line is optional, so we care about DEFER only */
    if (!bri->sda_gpiod) {
        /*
         * We have SCL. Pull SCL low and wait a bit so that SDA glitches
         * have no effect.
         */
        gpiod_direction_output(bri->scl_gpiod, 0);
        udelay(I2C_US_DELAY_COUNT_TEN);
        gpiod = devm_gpiod_get(dev, "sda", GPIOD_IN);

        /* Wait a bit in case of a SDA glitch, and then release SCL. */
        udelay(I2C_US_DELAY_COUNT_TEN);
        gpiod_direction_output(bri->scl_gpiod, 1);

        if (PTR_ERR(gpiod) == -EPROBE_DEFER) {
            ret = -EPROBE_DEFER;
            goto cleanup_pinctrl_state;
        }
        if (!IS_ERR(gpiod)) {
            bri->sda_gpiod = gpiod;
        }
    }

cleanup_pinctrl_state:
    /* change the state of the pins back to their default state */
    if (bri->pinctrl) {
        pinctrl_select_state(bri->pinctrl, bri->pins_default);
    }

    return ret;
}

static int i2c_gpio_init_recovery(struct i2c_adapter *adap)
{
    i2c_gpio_init_pinctrl_recovery(adap);
    return i2c_gpio_init_generic_recovery(adap);
}

static int i2c_init_recovery(struct i2c_adapter *adap)
{
    struct i2c_bus_recovery_info *bri = adap->bus_recovery_info;
    char *err_str, *err_level = KERN_ERR;

    if (!bri) {
        return 0;
    }

    if (i2c_gpio_init_recovery(adap) == -EPROBE_DEFER) {
        return -EPROBE_DEFER;
    }

    if (!bri->recover_bus) {
        err_str = "no suitable method provided";
        err_level = KERN_DEBUG;
        goto err;
    }

    if (bri->scl_gpiod && bri->recover_bus == i2c_generic_scl_recovery) {
        bri->get_scl = get_scl_gpio_value;
        bri->set_scl = set_scl_gpio_value;
        if (bri->sda_gpiod) {
            bri->get_sda = get_sda_gpio_value;
            /* add proper flag instead of '0' once available */
            if (gpiod_get_direction(bri->sda_gpiod) == 0) {
                bri->set_sda = set_sda_gpio_value;
            }
        }
    } else if (bri->recover_bus == i2c_generic_scl_recovery) {
        /* Generic SCL recovery */
        if (!bri->set_scl || !bri->get_scl) {
            err_str = "no {get|set}_scl() found";
            goto err;
        }
        if (!bri->set_sda && !bri->get_sda) {
            err_str = "either get_sda() or set_sda() needed";
            goto err;
        }
    }

    return 0;
err:
    dev_printk(err_level, &adap->dev, "Not using recovery: %s\n", err_str);
    adap->bus_recovery_info = NULL;

    return -EINVAL;
}

static int i2c_smbus_host_notify_to_irq(const struct i2c_client *client)
{
    struct i2c_adapter *adap = client->adapter;
    unsigned int irq;

    if (!adap->host_notify_domain) {
        return -ENXIO;
    }

    if (client->flags & I2C_CLIENT_TEN) {
        return -EINVAL;
    }

    irq = irq_create_mapping(adap->host_notify_domain, client->addr);

    return irq > 0 ? irq : -ENXIO;
}

static int i2c_device_probe(struct device *dev)
{
    struct i2c_client *client = i2c_verify_client(dev);
    struct i2c_driver *driver;
    int status;
    if (!client) {
        return 0;
    }
    client->irq = client->init_irq;
    if (!client->irq) {
        int irq = -ENOENT;
        if (client->flags & I2C_CLIENT_HOST_NOTIFY) {
            dev_dbg(dev, "Using Host Notify IRQ\n");
            /* Keep adapter active when Host Notify is required */
            pm_runtime_get_sync(&client->adapter->dev);
            irq = i2c_smbus_host_notify_to_irq(client);
        } else if (dev->of_node) {
            irq = of_irq_get_byname(dev->of_node, "irq");
            if (irq == -EINVAL || irq == -ENODATA) {
                irq = of_irq_get(dev->of_node, 0);
            }
        } else if (ACPI_COMPANION(dev)) {
            irq = i2c_acpi_get_irq(client);
        }
        if (irq == -EPROBE_DEFER) {
            status = irq;
            goto put_sync_adapter;
        }
        if (irq < 0) {
            irq = 0;
        }
        client->irq = irq;
    }
    driver = to_i2c_driver(dev->driver);
    /*
     * An I2C ID table is not mandatory, if and only if, a suitable OF
     * or ACPI ID table is supplied for the probing device.
     */
    if (!driver->id_table && !acpi_driver_match_device(dev, dev->driver) &&
        !i2c_of_match_device(dev->driver->of_match_table, client)) {
        status = -ENODEV;
        goto put_sync_adapter;
    }
    if (client->flags & I2C_CLIENT_WAKE) {
        int wakeirq;
        wakeirq = of_irq_get_byname(dev->of_node, "wakeup");
        if (wakeirq == -EPROBE_DEFER) {
            status = wakeirq;
            goto put_sync_adapter;
        }
        device_init_wakeup(&client->dev, true);
        if (wakeirq > 0 && wakeirq != client->irq) {
            status = dev_pm_set_dedicated_wake_irq(dev, wakeirq);
        } else if (client->irq > 0) {
            status = dev_pm_set_wake_irq(dev, client->irq);
        } else {
            status = 0;
        }
        if (status) {
            dev_warn(&client->dev, "failed to set up wakeup irq\n");
        }
    }
    dev_dbg(dev, "probe\n");
    status = of_clk_set_defaults(dev->of_node, false);
    if (status < 0) {
        goto err_clear_wakeup_irq;
    }
    status = dev_pm_domain_attach(&client->dev, true);
    if (status) {
        goto err_clear_wakeup_irq;
    }
    /*
     * When there are no more users of probe(),
     * rename probe_new to probe.
     */
    if (driver->probe_new) {
        status = driver->probe_new(client);
    } else if (driver->probe) {
        status = driver->probe(client, i2c_match_id(driver->id_table, client));
    } else {
        status = -EINVAL;
    }
    if (status) {
        goto err_detach_pm_domain;
    }
    return 0;

err_detach_pm_domain:
    dev_pm_domain_detach(&client->dev, true);
err_clear_wakeup_irq:
    dev_pm_clear_wake_irq(&client->dev);
    device_init_wakeup(&client->dev, false);
put_sync_adapter:
    if (client->flags & I2C_CLIENT_HOST_NOTIFY) {
        pm_runtime_put_sync(&client->adapter->dev);
    }

    return status;
}

static int i2c_device_remove(struct device *dev)
{
    struct i2c_client *client = i2c_verify_client(dev);
    struct i2c_driver *driver;
    int status = 0;

    if (!client || !dev->driver) {
        return 0;
    }

    driver = to_i2c_driver(dev->driver);
    if (driver->remove) {
        dev_dbg(dev, "remove\n");
        status = driver->remove(client);
    }

    dev_pm_domain_detach(&client->dev, true);

    dev_pm_clear_wake_irq(&client->dev);
    device_init_wakeup(&client->dev, false);

    client->irq = 0;
    if (client->flags & I2C_CLIENT_HOST_NOTIFY) {
        pm_runtime_put(&client->adapter->dev);
    }

    return status;
}

static void i2c_device_shutdown(struct device *dev)
{
    struct i2c_client *client = i2c_verify_client(dev);
    struct i2c_driver *driver;

    if (!client || !dev->driver) {
        return;
    }
    driver = to_i2c_driver(dev->driver);
    if (driver->shutdown) {
        driver->shutdown(client);
    } else if (client->irq > 0) {
        disable_irq(client->irq);
    }
}

static void i2c_client_dev_release(struct device *dev)
{
    kfree(to_i2c_client(dev));
}

static ssize_t name_show(struct device *dev, struct device_attribute *attr, char *buf)
{
    return sprintf(buf, "%s\n", dev->type == &i2c_client_type ? to_i2c_client(dev)->name : to_i2c_adapter(dev)->name);
}
static DEVICE_ATTR_RO(name);

static ssize_t modalias_show(struct device *dev, struct device_attribute *attr, char *buf)
{
    struct i2c_client *client = to_i2c_client(dev);
    int len;

    len = of_device_modalias(dev, buf, PAGE_SIZE);
    if (len != -ENODEV) {
        return len;
    }

    len = acpi_device_modalias(dev, buf, PAGE_SIZE - 1);
    if (len != -ENODEV) {
        return len;
    }

    return sprintf(buf, "%s%s\n", I2C_MODULE_PREFIX, client->name);
}
static DEVICE_ATTR_RO(modalias);

static struct attribute *i2c_dev_attrs[] = {&dev_attr_name.attr,
                                            /* modalias helps coldplug:  modprobe $(cat .../modalias) */
                                            &dev_attr_modalias.attr, NULL};
ATTRIBUTE_GROUPS(i2c_dev);

struct bus_type i2c_bus_type = {
    .name = "i2c",
    .match = i2c_device_match,
    .probe = i2c_device_probe,
    .remove = i2c_device_remove,
    .shutdown = i2c_device_shutdown,
};
EXPORT_SYMBOL_GPL(i2c_bus_type);

struct device_type i2c_client_type = {
    .groups = i2c_dev_groups,
    .uevent = i2c_device_uevent,
    .release = i2c_client_dev_release,
};
EXPORT_SYMBOL_GPL(i2c_client_type);

/**
 * i2c_verify_client - return parameter as i2c_client, or NULL
 * @dev: device, probably from some driver model iterator
 *
 * When traversing the driver model tree, perhaps using driver model
 * iterators like @device_for_each_child(), you can't assume very much
 * about the nodes you find.  Use this function to avoid oopses caused
 * by wrongly treating some non-I2C device as an i2c_client.
 */
struct i2c_client *i2c_verify_client(struct device *dev)
{
    return (dev->type == &i2c_client_type) ? to_i2c_client(dev) : NULL;
}
EXPORT_SYMBOL(i2c_verify_client);

/* Return a unique address which takes the flags of the client into account */
static unsigned short i2c_encode_flags_to_addr(struct i2c_client *client)
{
    unsigned short addr = client->addr;

    /* For some client flags, add an arbitrary offset to avoid collisions */
    if (client->flags & I2C_CLIENT_TEN) {
        addr |= I2C_ADDR_OFFSET_TEN_BIT;
    }

    if (client->flags & I2C_CLIENT_SLAVE) {
        addr |= I2C_ADDR_OFFSET_SLAVE;
    }

    return addr;
}

/* This is a permissive address validity check, I2C address map constraints
 * are purposely not enforced, except for the general call address. */
static int i2c_check_addr_validity(unsigned int addr, unsigned short flags)
{
    if (flags & I2C_CLIENT_TEN) {
        /* 10-bit address, all values are valid */
        if (addr > 0x3ff) {
            return -EINVAL;
        }
    } else {
        /* 7-bit address, reject the general call address */
        if (addr == 0x00 || addr > 0x7f) {
            return -EINVAL;
        }
    }
    return 0;
}

/* And this is a strict address validity check, used when probing. If a
 * device uses a reserved address, then it shouldn't be probed. 7-bit
 * addressing is assumed, 10-bit address devices are rare and should be
 * explicitly enumerated. */
int i2c_check_7bit_addr_validity_strict(unsigned short addr)
{
    /*
     * Reserved addresses per I2C specification:
     *  0x00       General call address / START byte
     *  0x01       CBUS address
     *  0x02       Reserved for different bus format
     *  0x03       Reserved for future purposes
     *  0x04-0x07  Hs-mode master code
     *  0x78-0x7b  10-bit slave addressing
     *  0x7c-0x7f  Reserved for future purposes
     */
    if (addr < 0x08 || addr > 0x77) {
        return -EINVAL;
    }
    return 0;
}

static int i2c_check_addr_busy_ext(struct device *dev, void *addrp)
{
    struct i2c_client *client = i2c_verify_client(dev);
    int addr = *(int *)addrp;

    if (client && i2c_encode_flags_to_addr(client) == addr) {
        return -EBUSY;
    }
    return 0;
}

/* walk up mux tree */
static int i2c_check_mux_parents(struct i2c_adapter *adapter, int addr)
{
    struct i2c_adapter *parent = i2c_parent_is_i2c_adapter(adapter);
    int result;
    result = device_for_each_child(&adapter->dev, &addr, i2c_check_addr_busy_ext);
    if (!result && parent) {
        result = i2c_check_mux_parents(parent, addr);
    }
    return result;
}

/* recurse down mux tree */
static int i2c_check_mux_children(struct device *dev, void *addrp)
{
    int result;

    if (dev->type == &i2c_adapter_type) {
        result = device_for_each_child(dev, addrp, i2c_check_mux_children);
    } else {
        result = i2c_check_addr_busy_ext(dev, addrp);
    }

    return result;
}

static int i2c_check_addr_busy(struct i2c_adapter *adapter, int addr)
{
    struct i2c_adapter *parent = i2c_parent_is_i2c_adapter(adapter);
    int result = 0;

    if (parent) {
        result = i2c_check_mux_parents(parent, addr);
    }

    if (!result) {
        result = device_for_each_child(&adapter->dev, &addr, i2c_check_mux_children);
    }

    return result;
}

/**
 * i2c_adapter_lock_bus - Get exclusive access to an I2C bus segment
 * @adapter: Target I2C bus segment
 * @flags: I2C_LOCK_ROOT_ADAPTER locks the root i2c adapter, I2C_LOCK_SEGMENT
 *    locks only this branch in the adapter tree
 */
static void i2c_adapter_lock_bus(struct i2c_adapter *adapter, unsigned int flags)
{
    rt_mutex_lock_nested(&adapter->bus_lock, i2c_adapter_depth(adapter));
}

/**
 * i2c_adapter_trylock_bus - Try to get exclusive access to an I2C bus segment
 * @adapter: Target I2C bus segment
 * @flags: I2C_LOCK_ROOT_ADAPTER trylocks the root i2c adapter, I2C_LOCK_SEGMENT
 *    trylocks only this branch in the adapter tree
 */
static int i2c_adapter_trylock_bus(struct i2c_adapter *adapter, unsigned int flags)
{
    return rt_mutex_trylock(&adapter->bus_lock);
}

/**
 * i2c_adapter_unlock_bus - Release exclusive access to an I2C bus segment
 * @adapter: Target I2C bus segment
 * @flags: I2C_LOCK_ROOT_ADAPTER unlocks the root i2c adapter, I2C_LOCK_SEGMENT
 *    unlocks only this branch in the adapter tree
 */
static void i2c_adapter_unlock_bus(struct i2c_adapter *adapter, unsigned int flags)
{
    rt_mutex_unlock(&adapter->bus_lock);
}

static void i2c_dev_set_name(struct i2c_adapter *adap, struct i2c_client *client, struct i2c_board_info const *info,
                             int status)
{
    struct acpi_device *adev = ACPI_COMPANION(&client->dev);

    if (info && info->dev_name) {
        dev_set_name(&client->dev, "i2c-%s", info->dev_name);
        return;
    }

    if (adev) {
        dev_set_name(&client->dev, "i2c-%s", acpi_dev_name(adev));
        return;
    }

    if (status == 0) {
        dev_set_name(&client->dev, "%d-%04x", i2c_adapter_id(adap), i2c_encode_flags_to_addr(client));
    } else {
        dev_set_name(&client->dev, "%d-%04x-%01x", i2c_adapter_id(adap), i2c_encode_flags_to_addr(client), status);
    }
}

int i2c_dev_irq_from_resources(const struct resource *resources, unsigned int num_resources)
{
    struct irq_data *irqd;
    int i;

    for (i = 0; i < num_resources; i++) {
        const struct resource *r = &resources[i];

        if (resource_type(r) != IORESOURCE_IRQ) {
            continue;
        }

        if (r->flags & IORESOURCE_BITS) {
            irqd = irq_get_irq_data(r->start);
            if (!irqd) {
                break;
            }

            irqd_set_trigger_type(irqd, r->flags & IORESOURCE_BITS);
        }

        return r->start;
    }

    return 0;
}

/**
 * i2c_new_client_device - instantiate an i2c device
 * @adap: the adapter managing the device
 * @info: describes one I2C device; bus_num is ignored
 * Context: can sleep
 *
 * Create an i2c device. Binding is handled through driver model
 * probe()/remove() methods.  A driver may be bound to this device when we
 * return from this function, or any later moment (e.g. maybe hotplugging will
 * load the driver module).  This call is not appropriate for use by mainboard
 * initialization logic, which usually runs during an arch_initcall() long
 * before any i2c_adapter could exist.
 *
 * This returns the new i2c client, which may be saved for later use with
 * i2c_unregister_device(); or an ERR_PTR to describe the error.
 */
#define I2C_NEW_CLIENT_TEN 10
#define I2C_NEW_CLIENT_SEVEN 7
struct i2c_client *i2c_new_client_device(struct i2c_adapter *adap, struct i2c_board_info const *info)
{
    struct i2c_client *client;
    int status;

    client = kzalloc(sizeof(*client), GFP_KERNEL);
    if (!client) {
        return ERR_PTR(-ENOMEM);
    }

    client->adapter = adap;

    client->dev.platform_data = info->platform_data;
    client->flags = info->flags;
    client->addr = info->addr;

    client->init_irq = info->irq;
    if (!client->init_irq) {
        client->init_irq = i2c_dev_irq_from_resources(info->resources, info->num_resources);
    }

    strlcpy(client->name, info->type, sizeof(client->name));

    status = i2c_check_addr_validity(client->addr, client->flags);
    if (status) {
        dev_err(&adap->dev, "Invalid %d-bit I2C address 0x%02hx\n",
                client->flags & I2C_CLIENT_TEN ? I2C_NEW_CLIENT_TEN : I2C_NEW_CLIENT_SEVEN, client->addr);
        goto out_err_silent;
    }

    /* Check for address business */
    status = i2c_check_addr_ex(adap, i2c_encode_flags_to_addr(client));
    if (status) {
        dev_err(&adap->dev, "%d i2c clients have been registered at 0x%02x", status, client->addr);
    }

    client->dev.parent = &client->adapter->dev;
    client->dev.bus = &i2c_bus_type;
    client->dev.type = &i2c_client_type;
    client->dev.of_node = of_node_get(info->of_node);
    client->dev.fwnode = info->fwnode;

    i2c_dev_set_name(adap, client, info, status);

    if (info->properties) {
        status = device_add_properties(&client->dev, info->properties);
        if (status) {
            dev_err(&adap->dev, "Failed to add properties to client %s: %d\n", client->name, status);
            goto out_err_put_of_node;
        }
    }

    status = device_register(&client->dev);
    if (status) {
        goto out_free_props;
    }

    dev_dbg(&adap->dev, "client [%s] registered with bus id %s\n", client->name, dev_name(&client->dev));

    return client;

out_free_props:
    if (info->properties) {
        device_remove_properties(&client->dev);
    }
out_err_put_of_node:
    of_node_put(info->of_node);
out_err_silent:
    kfree(client);
    return ERR_PTR(status);
}
EXPORT_SYMBOL_GPL(i2c_new_client_device);

/**
 * i2c_unregister_device - reverse effect of i2c_new_*_device()
 * @client: value returned from i2c_new_*_device()
 * Context: can sleep
 */
void i2c_unregister_device(struct i2c_client *client)
{
    if (IS_ERR_OR_NULL(client)) {
        return;
    }

    if (client->dev.of_node) {
        of_node_clear_flag(client->dev.of_node, OF_POPULATED);
        of_node_put(client->dev.of_node);
    }

    if (ACPI_COMPANION(&client->dev)) {
        acpi_device_clear_enumerated(ACPI_COMPANION(&client->dev));
    }
    device_unregister(&client->dev);
}
EXPORT_SYMBOL_GPL(i2c_unregister_device);

static const struct i2c_device_id dummy_id[] = {
    {"dummy", 0},
    {},
};

static int dummy_probe(struct i2c_client *client, const struct i2c_device_id *id)
{
    return 0;
}

static int dummy_remove(struct i2c_client *client)
{
    return 0;
}

static struct i2c_driver dummy_driver = {
    .driver.name = "dummy",
    .probe = dummy_probe,
    .remove = dummy_remove,
    .id_table = dummy_id,
};

/**
 * i2c_new_dummy_device - return a new i2c device bound to a dummy driver
 * @adapter: the adapter managing the device
 * @address: seven bit address to be used
 * Context: can sleep
 *
 * This returns an I2C client bound to the "dummy" driver, intended for use
 * with devices that consume multiple addresses.  Examples of such chips
 * include various EEPROMS (like 24c04 and 24c08 models).
 *
 * These dummy devices have two main uses.  First, most I2C and SMBus calls
 * except i2c_transfer() need a client handle; the dummy will be that handle.
 * And second, this prevents the specified address from being bound to a
 * different driver.
 *
 * This returns the new i2c client, which should be saved for later use with
 * i2c_unregister_device(); or an ERR_PTR to describe the error.
 */
struct i2c_client *i2c_new_dummy_device(struct i2c_adapter *adapter, u16 address)
{
    struct i2c_board_info info = {
        I2C_BOARD_INFO("dummy", address),
    };

    return i2c_new_client_device(adapter, &info);
}
EXPORT_SYMBOL_GPL(i2c_new_dummy_device);

struct i2c_dummy_devres {
    struct i2c_client *client;
};

static void devm_i2c_release_dummy(struct device *dev, void *res)
{
    struct i2c_dummy_devres *this = res;

    i2c_unregister_device(this->client);
}

/**
 * devm_i2c_new_dummy_device - return a new i2c device bound to a dummy driver
 * @dev: device the managed resource is bound to
 * @adapter: the adapter managing the device
 * @address: seven bit address to be used
 * Context: can sleep
 *
 * This is the device-managed version of @i2c_new_dummy_device. It returns the
 * new i2c client or an ERR_PTR in case of an error.
 */
struct i2c_client *devm_i2c_new_dummy_device(struct device *dev, struct i2c_adapter *adapter, u16 address)
{
    struct i2c_dummy_devres *dr;
    struct i2c_client *client;

    dr = devres_alloc(devm_i2c_release_dummy, sizeof(*dr), GFP_KERNEL);
    if (!dr) {
        return ERR_PTR(-ENOMEM);
    }

    client = i2c_new_dummy_device(adapter, address);
    if (IS_ERR(client)) {
        devres_free(dr);
    } else {
        dr->client = client;
        devres_add(dev, dr);
    }

    return client;
}
EXPORT_SYMBOL_GPL(devm_i2c_new_dummy_device);

/**
 * i2c_new_ancillary_device - Helper to get the instantiated secondary address
 * and create the associated device
 * @client: Handle to the primary client
 * @name: Handle to specify which secondary address to get
 * @default_addr: Used as a fallback if no secondary address was specified
 * Context: can sleep
 *
 * I2C clients can be composed of multiple I2C slaves bound together in a single
 * component. The I2C client driver then binds to the master I2C slave and needs
 * to create I2C dummy clients to communicate with all the other slaves.
 *
 * This function creates and returns an I2C dummy client whose I2C address is
 * retrieved from the platform firmware based on the given slave name. If no
 * address is specified by the firmware default_addr is used.
 *
 * On DT-based platforms the address is retrieved from the "reg" property entry
 * cell whose "reg-names" value matches the slave name.
 *
 * This returns the new i2c client, which should be saved for later use with
 * i2c_unregister_device(); or an ERR_PTR to describe the error.
 */
struct i2c_client *i2c_new_ancillary_device(struct i2c_client *client, const char *name, u16 default_addr)
{
    struct device_node *np = client->dev.of_node;
    u32 addr = default_addr;
    int i;

    if (np) {
        i = of_property_match_string(np, "reg-names", name);
        if (i >= 0) {
            of_property_read_u32_index(np, "reg", i, &addr);
        }
    }

    dev_dbg(&client->adapter->dev, "Address for %s : 0x%x\n", name, addr);
    return i2c_new_dummy_device(client->adapter, addr);
}
EXPORT_SYMBOL_GPL(i2c_new_ancillary_device);

/* ------------------------------------------------------------------------- */

/* I2C bus adapters -- one roots each I2C or SMBUS segment */

static void i2c_adapter_dev_release(struct device *dev)
{
    struct i2c_adapter *adap = to_i2c_adapter(dev);
    complete(&adap->dev_released);
}

unsigned int i2c_adapter_depth(struct i2c_adapter *adapter)
{
    unsigned int depth = 0;

    while ((adapter = i2c_parent_is_i2c_adapter(adapter))) {
        depth++;
    }

    WARN_ONCE(depth >= MAX_LOCKDEP_SUBCLASSES, "adapter depth exceeds lockdep subclass limit\n");

    return depth;
}
EXPORT_SYMBOL_GPL(i2c_adapter_depth);

/*
 * Let users instantiate I2C devices through sysfs. This can be used when
 * platform initialization code doesn't contain the proper data for
 * whatever reason. Also useful for drivers that do device detection and
 * detection fails, either because the device uses an unexpected address,
 * or this is a compatible device with different ID register values.
 *
 * Parameter checking may look overzealous, but we really don't want
 * the user to provide incorrect parameters.
 */
static ssize_t new_device_store(struct device *dev, struct device_attribute *attr, const char *buf, size_t count)
{
    struct i2c_adapter *adap = to_i2c_adapter(dev);
    struct i2c_board_info info;
    struct i2c_client *client;
    char *blank, end;
    int res;

    memset(&info, 0, sizeof(struct i2c_board_info));

    blank = strchr(buf, ' ');
    if (!blank) {
        dev_err(dev, "%s: Missing parameters\n", "new_device");
        return -EINVAL;
    }
    if (blank - buf > I2C_NAME_SIZE - 1) {
        dev_err(dev, "%s: Invalid device name\n", "new_device");
        return -EINVAL;
    }
    memcpy(info.type, buf, blank - buf);

    /* Parse remaining parameters, reject extra parameters */
    res = sscanf(++blank, "%hi%c", &info.addr, &end);
    if (res < 1) {
        dev_err(dev, "%s: Can't parse I2C address\n", "new_device");
        return -EINVAL;
    }
    if (res > 1 && end != '\n') {
        dev_err(dev, "%s: Extra parameters\n", "new_device");
        return -EINVAL;
    }

    if ((info.addr & I2C_ADDR_OFFSET_TEN_BIT) == I2C_ADDR_OFFSET_TEN_BIT) {
        info.addr &= ~I2C_ADDR_OFFSET_TEN_BIT;
        info.flags |= I2C_CLIENT_TEN;
    }

    if (info.addr & I2C_ADDR_OFFSET_SLAVE) {
        info.addr &= ~I2C_ADDR_OFFSET_SLAVE;
        info.flags |= I2C_CLIENT_SLAVE;
    }

    client = i2c_new_client_device(adap, &info);
    if (IS_ERR(client)) {
        return PTR_ERR(client);
    }

    /* Keep track of the added device */
    mutex_lock(&adap->userspace_clients_lock);
    list_add_tail(&client->detected, &adap->userspace_clients);
    mutex_unlock(&adap->userspace_clients_lock);
    dev_info(dev, "%s: Instantiated device %s at 0x%02hx\n", "new_device", info.type, info.addr);

    return count;
}
static DEVICE_ATTR_WO(new_device);

/*
 * And of course let the users delete the devices they instantiated, if
 * they got it wrong. This interface can only be used to delete devices
 * instantiated by i2c_sysfs_new_device above. This guarantees that we
 * don't delete devices to which some kernel code still has references.
 *
 * Parameter checking may look overzealous, but we really don't want
 * the user to delete the wrong device.
 */
static ssize_t delete_device_store(struct device *dev, struct device_attribute *attr, const char *buf, size_t count)
{
    struct i2c_adapter *adap = to_i2c_adapter(dev);
    struct i2c_client *client, *next;
    unsigned short addr;
    char end;
    int res;

    /* Parse parameters, reject extra parameters */
    res = sscanf(buf, "%hi%c", &addr, &end);
    if (res < 1) {
        dev_err(dev, "%s: Can't parse I2C address\n", "delete_device");
        return -EINVAL;
    }
    if (res > 1 && end != '\n') {
        dev_err(dev, "%s: Extra parameters\n", "delete_device");
        return -EINVAL;
    }

    /* Make sure the device was added through sysfs */
    res = -ENOENT;
    mutex_lock_nested(&adap->userspace_clients_lock, i2c_adapter_depth(adap));
    list_for_each_entry_safe(client, next, &adap->userspace_clients, detected)
    {
        if (i2c_encode_flags_to_addr(client) == addr) {
            dev_info(dev, "%s: Deleting device %s at 0x%02hx\n", "delete_device", client->name, client->addr);

            list_del(&client->detected);
            i2c_unregister_device(client);
            res = count;
            break;
        }
    }
    mutex_unlock(&adap->userspace_clients_lock);

    if (res < 0) {
        dev_err(dev, "%s: Can't find device in list\n", "delete_device");
    }
    return res;
}
static DEVICE_ATTR_IGNORE_LOCKDEP(delete_device, S_IWUSR, NULL, delete_device_store);

static struct attribute *i2c_adapter_attrs[] = {&dev_attr_name.attr, &dev_attr_new_device.attr,
                                                &dev_attr_delete_device.attr, NULL};
ATTRIBUTE_GROUPS(i2c_adapter);

struct device_type i2c_adapter_type = {
    .groups = i2c_adapter_groups,
    .release = i2c_adapter_dev_release,
};
EXPORT_SYMBOL_GPL(i2c_adapter_type);

/**
 * i2c_verify_adapter - return parameter as i2c_adapter or NULL
 * @dev: device, probably from some driver model iterator
 *
 * When traversing the driver model tree, perhaps using driver model
 * iterators like @device_for_each_child(), you can't assume very much
 * about the nodes you find.  Use this function to avoid oopses caused
 * by wrongly treating some non-I2C device as an i2c_adapter.
 */
struct i2c_adapter *i2c_verify_adapter(struct device *dev)
{
    return (dev->type == &i2c_adapter_type) ? to_i2c_adapter(dev) : NULL;
}
EXPORT_SYMBOL(i2c_verify_adapter);

#ifdef CONFIG_I2C_COMPAT
static struct class_compat *i2c_adapter_compat_class;
#endif

static void i2c_scan_static_board_info(struct i2c_adapter *adapter)
{
    struct i2c_devinfo *devinfo;

    down_read(&__i2c_board_lock);
    list_for_each_entry(devinfo, &__i2c_board_list, list)
    {
        if (devinfo->busnum == adapter->nr && IS_ERR(i2c_new_client_device(adapter, &devinfo->board_info))) {
            dev_err(&adapter->dev, "Can't create device at 0x%02x\n", devinfo->board_info.addr);
        }
    }
    up_read(&__i2c_board_lock);
}

static int i2c_do_add_adapter(struct i2c_driver *driver, struct i2c_adapter *adap)
{
    /* Detect supported devices on that bus, and instantiate them */
    i2c_detect(adap, driver);

    return 0;
}

static int process_new_adapter_ext(struct device_driver *d, void *data)
{
    return i2c_do_add_adapter(to_i2c_driver(d), data);
}

static const struct i2c_lock_operations i2c_adapter_lock_ops = {
    .lock_bus = i2c_adapter_lock_bus,
    .trylock_bus = i2c_adapter_trylock_bus,
    .unlock_bus = i2c_adapter_unlock_bus,
};

static void i2c_host_notify_irq_teardown(struct i2c_adapter *adap)
{
    struct irq_domain *domain = adap->host_notify_domain;
    irq_hw_number_t hwirq;

    if (!domain) {
        return;
    }

    for (hwirq = 0; hwirq < I2C_ADDR_7BITS_COUNT; hwirq++) {
        irq_dispose_mapping(irq_find_mapping(domain, hwirq));
    }

    irq_domain_remove(domain);
    adap->host_notify_domain = NULL;
}

static int i2c_host_notify_irq_map(struct irq_domain *h, unsigned int virq, irq_hw_number_t hw_irq_num)
{
    irq_set_chip_and_handler(virq, &dummy_irq_chip, handle_simple_irq);

    return 0;
}

static const struct irq_domain_ops i2c_host_notify_irq_ops = {
    .map = i2c_host_notify_irq_map,
};

static int i2c_setup_host_notify_irq_domain(struct i2c_adapter *adap)
{
    struct irq_domain *domain;

    if (!i2c_check_functionality(adap, I2C_FUNC_SMBUS_HOST_NOTIFY)) {
        return 0;
    }

    domain = irq_domain_create_linear(adap->dev.parent->fwnode, I2C_ADDR_7BITS_COUNT, &i2c_host_notify_irq_ops, adap);
    if (!domain) {
        return -ENOMEM;
    }

    adap->host_notify_domain = domain;

    return 0;
}

/**
 * i2c_handle_smbus_host_notify - Forward a Host Notify event to the correct
 * I2C client.
 * @adap: the adapter
 * @addr: the I2C address of the notifying device
 * Context: can't sleep
 *
 * Helper function to be called from an I2C bus driver's interrupt
 * handler. It will schedule the Host Notify IRQ.
 */
int i2c_handle_smbus_host_notify(struct i2c_adapter *adap, unsigned short addr)
{
    int irq;

    if (!adap) {
        return -EINVAL;
    }

    irq = irq_find_mapping(adap->host_notify_domain, addr);
    if (irq <= 0) {
        return -ENXIO;
    }

    generic_handle_irq(irq);

    return 0;
}
EXPORT_SYMBOL_GPL(i2c_handle_smbus_host_notify);

static int i2c_register_adapter(struct i2c_adapter *adap)
{
    int res = -EINVAL;

    /* Can't register until after driver model init */
    if (WARN_ON(!is_registered)) {
        res = -EAGAIN;
        goto out_list;
    }

    /* Sanity checks */
    if (WARN(!adap->name[0], "i2c adapter has no name")) {
        goto out_list;
    }

    if (!adap->algo) {
        pr_err("adapter '%s': no algo supplied!\n", adap->name);
        goto out_list;
    }

    if (!adap->lock_ops) {
        adap->lock_ops = &i2c_adapter_lock_ops;
    }

    adap->locked_flags = 0;
    rt_mutex_init(&adap->bus_lock);
    rt_mutex_init(&adap->mux_lock);
    mutex_init(&adap->userspace_clients_lock);
    INIT_LIST_HEAD(&adap->userspace_clients);

    /* Set default timeout to 1 second if not already set */
    if (adap->timeout == 0) {
        adap->timeout = HZ;
    }

    /* register soft irqs for Host Notify */
    res = i2c_setup_host_notify_irq_domain(adap);
    if (res) {
        pr_err("adapter '%s': can't create Host Notify IRQs (%d)\n", adap->name, res);
        goto out_list;
    }

    dev_set_name(&adap->dev, "i2c-%d", adap->nr);
    adap->dev.bus = &i2c_bus_type;
    adap->dev.type = &i2c_adapter_type;
    res = device_register(&adap->dev);
    if (res) {
        pr_err("adapter '%s': can't register device (%d)\n", adap->name, res);
        goto out_list;
    }

    res = of_i2c_setup_smbus_alert(adap);
    if (res) {
        goto out_reg;
    }

    pm_runtime_no_callbacks(&adap->dev);
    pm_suspend_ignore_children(&adap->dev, true);
    pm_runtime_enable(&adap->dev);

    res = i2c_init_recovery(adap);
    if (res == -EPROBE_DEFER) {
        goto out_reg;
    }

    dev_dbg(&adap->dev, "adapter [%s] registered\n", adap->name);

#ifdef CONFIG_I2C_COMPAT
    res = class_compat_create_link(i2c_adapter_compat_class, &adap->dev, adap->dev.parent);
    if (res) {
        dev_warn(&adap->dev, "Failed to create compatibility class link\n");
    }
#endif

    /* create pre-declared device nodes */
    of_i2c_register_devices(adap);
    i2c_acpi_install_space_handler(adap);
    i2c_acpi_register_devices(adap);

    if (adap->nr < __i2c_first_dynamic_bus_num) {
        i2c_scan_static_board_info(adap);
    }

    /* Notify drivers */
    mutex_lock(&core_lock);
    bus_for_each_drv(&i2c_bus_type, NULL, adap, process_new_adapter_ext);
    mutex_unlock(&core_lock);

    return 0;

out_reg:
    init_completion(&adap->dev_released);
    device_unregister(&adap->dev);
    wait_for_completion(&adap->dev_released);
out_list:
    mutex_lock(&core_lock);
    idr_remove(&i2c_adapter_idr, adap->nr);
    mutex_unlock(&core_lock);
    return res;
}

/**
 * i2c_add_numbered_adapter_ext - i2c_add_numbered_adapter where nr is never -1
 * @adap: the adapter to register (with adap->nr initialized)
 * Context: can sleep
 *
 * See i2c_add_numbered_adapter() for details.
 */
static int i2c_add_numbered_adapter_ext(struct i2c_adapter *adap)
{
    int id;

    mutex_lock(&core_lock);
    id = idr_alloc(&i2c_adapter_idr, adap, adap->nr, adap->nr + 1, GFP_KERNEL);
    mutex_unlock(&core_lock);
    if (WARN(id < 0, "couldn't get idr")) {
        return id == -ENOSPC ? -EBUSY : id;
    }

    return i2c_register_adapter(adap);
}

/**
 * i2c_add_adapter - declare i2c adapter, use dynamic bus number
 * @adapter: the adapter to add
 * Context: can sleep
 *
 * This routine is used to declare an I2C adapter when its bus number
 * doesn't matter or when its bus number is specified by an dt alias.
 * Examples of bases when the bus number doesn't matter: I2C adapters
 * dynamically added by USB links or PCI plugin cards.
 *
 * When this returns zero, a new bus number was allocated and stored
 * in adap->nr, and the specified adapter became available for clients.
 * Otherwise, a negative errno value is returned.
 */
int i2c_add_adapter(struct i2c_adapter *adapter)
{
    struct device *dev = &adapter->dev;
    int id;

    if (dev->of_node) {
        id = of_alias_get_id(dev->of_node, "i2c");
        if (id >= 0) {
            adapter->nr = id;
            return i2c_add_numbered_adapter_ext(adapter);
        }
    }

    mutex_lock(&core_lock);
    id = idr_alloc(&i2c_adapter_idr, adapter, __i2c_first_dynamic_bus_num, 0, GFP_KERNEL);
    mutex_unlock(&core_lock);
    if (WARN(id < 0, "couldn't get idr")) {
        return id;
    }

    adapter->nr = id;

    return i2c_register_adapter(adapter);
}
EXPORT_SYMBOL(i2c_add_adapter);

/**
 * i2c_add_numbered_adapter - declare i2c adapter, use static bus number
 * @adap: the adapter to register (with adap->nr initialized)
 * Context: can sleep
 *
 * This routine is used to declare an I2C adapter when its bus number
 * matters.  For example, use it for I2C adapters from system-on-chip CPUs,
 * or otherwise built in to the system's mainboard, and where i2c_board_info
 * is used to properly configure I2C devices.
 *
 * If the requested bus number is set to -1, then this function will behave
 * identically to i2c_add_adapter, and will dynamically assign a bus number.
 *
 * If no devices have pre-been declared for this bus, then be sure to
 * register the adapter before any dynamically allocated ones.  Otherwise
 * the required bus ID may not be available.
 *
 * When this returns zero, the specified adapter became available for
 * clients using the bus number provided in adap->nr.  Also, the table
 * of I2C devices pre-declared using i2c_register_board_info() is scanned,
 * and the appropriate driver model device nodes are created.  Otherwise, a
 * negative errno value is returned.
 */
int i2c_add_numbered_adapter(struct i2c_adapter *adap)
{
    if (adap->nr == -1) { /* -1 means dynamically assign bus id */
        return i2c_add_adapter(adap);
    }

    return i2c_add_numbered_adapter_ext(adap);
}
EXPORT_SYMBOL_GPL(i2c_add_numbered_adapter);

static void i2c_do_del_adapter(struct i2c_driver *driver, struct i2c_adapter *adapter)
{
    struct i2c_client *client, *_n;

    /* Remove the devices we created ourselves as the result of hardware
     * probing (using a driver's detect method) */
    list_for_each_entry_safe(client, _n, &driver->clients, detected)
    {
        if (client->adapter == adapter) {
            dev_dbg(&adapter->dev, "Removing %s at 0x%x\n", client->name, client->addr);
            list_del(&client->detected);
            i2c_unregister_device(client);
        }
    }
}

static int unregister_client_ext(struct device *dev, void *dummy)
{
    struct i2c_client *client = i2c_verify_client(dev);
    if (client && strcmp(client->name, "dummy")) {
        i2c_unregister_device(client);
    }
    return 0;
}

static int unregister_dummy_ext(struct device *dev, void *dummy)
{
    struct i2c_client *client = i2c_verify_client(dev);
    i2c_unregister_device(client);
    return 0;
}

static int process_removed_adapter_ext(struct device_driver *d, void *data)
{
    i2c_do_del_adapter(to_i2c_driver(d), data);
    return 0;
}

/**
 * i2c_del_adapter - unregister I2C adapter
 * @adap: the adapter being unregistered
 * Context: can sleep
 *
 * This unregisters an I2C adapter which was previously registered
 * by @i2c_add_adapter or @i2c_add_numbered_adapter.
 */
void i2c_del_adapter(struct i2c_adapter *adap)
{
    struct i2c_adapter *found;
    struct i2c_client *client, *next;

    /* First make sure that this adapter was ever added */
    mutex_lock(&core_lock);
    found = idr_find(&i2c_adapter_idr, adap->nr);
    mutex_unlock(&core_lock);
    if (found != adap) {
        pr_debug("attempting to delete unregistered adapter [%s]\n", adap->name);
        return;
    }

    i2c_acpi_remove_space_handler(adap);
    /* Tell drivers about this removal */
    mutex_lock(&core_lock);
    bus_for_each_drv(&i2c_bus_type, NULL, adap, process_removed_adapter_ext);
    mutex_unlock(&core_lock);

    /* Remove devices instantiated from sysfs */
    mutex_lock_nested(&adap->userspace_clients_lock, i2c_adapter_depth(adap));
    list_for_each_entry_safe(client, next, &adap->userspace_clients, detected)
    {
        dev_dbg(&adap->dev, "Removing %s at 0x%x\n", client->name, client->addr);
        list_del(&client->detected);
        i2c_unregister_device(client);
    }
    mutex_unlock(&adap->userspace_clients_lock);

    /* Detach any active clients. This can't fail, thus we do not
     * check the returned value. This is a two-pass process, because
     * we can't remove the dummy devices during the first pass: they
     * could have been instantiated by real devices wishing to clean
     * them up properly, so we give them a chance to do that first. */
    device_for_each_child(&adap->dev, NULL, unregister_client_ext);
    device_for_each_child(&adap->dev, NULL, unregister_dummy_ext);

#ifdef CONFIG_I2C_COMPAT
    class_compat_remove_link(i2c_adapter_compat_class, &adap->dev, adap->dev.parent);
#endif

    /* device name is gone after device_unregister */
    dev_dbg(&adap->dev, "adapter [%s] unregistered\n", adap->name);

    pm_runtime_disable(&adap->dev);

    i2c_host_notify_irq_teardown(adap);

    /* wait until all references to the device are gone
     *
     * This is old code and should ideally be replaced by an
     * alternative which results in decoupling the lifetime of the struct
     * device from the i2c_adapter, like spi or netdev do. Any solution
     * should be thoroughly tested with DEBUG_KOBJECT_RELEASE enabled!
     */
    init_completion(&adap->dev_released);
    device_unregister(&adap->dev);
    wait_for_completion(&adap->dev_released);

    /* free bus id */
    mutex_lock(&core_lock);
    idr_remove(&i2c_adapter_idr, adap->nr);
    mutex_unlock(&core_lock);

    /* Clear the device structure in case this adapter is ever going to be
       added again */
    memset(&adap->dev, 0, sizeof(adap->dev));
}
EXPORT_SYMBOL(i2c_del_adapter);

static void i2c_parse_timing(struct device *dev, char *prop_name, u32 *cur_val_p, u32 def_val, bool use_def)
{
    int ret;

    ret = device_property_read_u32(dev, prop_name, cur_val_p);
    if (ret && use_def) {
        *cur_val_p = def_val;
    }

    dev_dbg(dev, "%s: %u\n", prop_name, *cur_val_p);
}

/**
 * i2c_parse_fw_timings - get I2C related timing parameters from firmware
 * @dev: The device to scan for I2C timing properties
 * @t: the i2c_timings struct to be filled with values
 * @use_defaults: bool to use sane defaults derived from the I2C specification
 *          when properties are not found, otherwise don't update
 *
 * Scan the device for the generic I2C properties describing timing parameters
 * for the signal and fill the given struct with the results. If a property was
 * not found and use_defaults was true, then maximum timings are assumed which
 * are derived from the I2C specification. If use_defaults is not used, the
 * results will be as before, so drivers can apply their own defaults before
 * calling this helper. The latter is mainly intended for avoiding regressions
 * of existing drivers which want to switch to this function. New drivers
 * almost always should use the defaults.
 */
#define I2C_BUS_FREQ_ONE_THOUSAND 1000
#define I2C_BUS_FREQ_THREE_HUNDRED 300
#define I2C_BUS_FREQ_ONE_HUNDRED_TWENTY 120

void i2c_parse_fw_timings(struct device *dev, struct i2c_timings *t, bool use_defaults)
{
    bool u = use_defaults;
    u32 d;

    i2c_parse_timing(dev, "clock-frequency", &t->bus_freq_hz, I2C_MAX_STANDARD_MODE_FREQ, u);

    d = t->bus_freq_hz <= I2C_MAX_STANDARD_MODE_FREQ ? I2C_BUS_FREQ_ONE_THOUSAND
        : t->bus_freq_hz <= I2C_MAX_FAST_MODE_FREQ   ? I2C_BUS_FREQ_THREE_HUNDRED
                                                     : I2C_BUS_FREQ_ONE_HUNDRED_TWENTY;
    i2c_parse_timing(dev, "i2c-scl-rising-time-ns", &t->scl_rise_ns, d, u);

    d = t->bus_freq_hz <= I2C_MAX_FAST_MODE_FREQ ? I2C_BUS_FREQ_THREE_HUNDRED : I2C_BUS_FREQ_ONE_HUNDRED_TWENTY;
    i2c_parse_timing(dev, "i2c-scl-falling-time-ns", &t->scl_fall_ns, d, u);

    i2c_parse_timing(dev, "i2c-scl-internal-delay-ns", &t->scl_int_delay_ns, 0, u);
    i2c_parse_timing(dev, "i2c-sda-falling-time-ns", &t->sda_fall_ns, t->scl_fall_ns, u);
    i2c_parse_timing(dev, "i2c-sda-hold-time-ns", &t->sda_hold_ns, 0, u);
    i2c_parse_timing(dev, "i2c-digital-filter-width-ns", &t->digital_filter_width_ns, 0, u);
    i2c_parse_timing(dev, "i2c-analog-filter-cutoff-frequency", &t->analog_filter_cutoff_freq_hz, 0, u);
}
EXPORT_SYMBOL_GPL(i2c_parse_fw_timings);

/* ------------------------------------------------------------------------- */

int i2c_for_each_dev(void *data, int (*fn)(struct device *dev, void *data))
{
    int res;

    mutex_lock(&core_lock);
    res = bus_for_each_dev(&i2c_bus_type, NULL, data, fn);
    mutex_unlock(&core_lock);

    return res;
}
EXPORT_SYMBOL_GPL(i2c_for_each_dev);

static int process_new_driver_ext(struct device *dev, void *data)
{
    if (dev->type != &i2c_adapter_type) {
        return 0;
    }
    return i2c_do_add_adapter(data, to_i2c_adapter(dev));
}

/*
 * An i2c_driver is used with one or more i2c_client (device) nodes to access
 * i2c slave chips, on a bus instance associated with some i2c_adapter.
 */

int i2c_register_driver(struct module *owner, struct i2c_driver *driver)
{
    int res;

    /* Can't register until after driver model init */
    if (WARN_ON(!is_registered)) {
        return -EAGAIN;
    }

    /* add the driver to the list of i2c drivers in the driver core */
    driver->driver.owner = owner;
    driver->driver.bus = &i2c_bus_type;
    INIT_LIST_HEAD(&driver->clients);

    /* When registration returns, the driver core
     * will have called probe() for all matching-but-unbound devices.
     */
    res = driver_register(&driver->driver);
    if (res) {
        return res;
    }

    pr_debug("driver [%s] registered\n", driver->driver.name);

    /* Walk the adapters that are already present */
    i2c_for_each_dev(driver, process_new_driver_ext);

    return 0;
}
EXPORT_SYMBOL(i2c_register_driver);

static int process_removed_driver_ext(struct device *dev, void *data)
{
    if (dev->type == &i2c_adapter_type) {
        i2c_do_del_adapter(data, to_i2c_adapter(dev));
    }
    return 0;
}

/**
 * i2c_del_driver - unregister I2C driver
 * @driver: the driver being unregistered
 * Context: can sleep
 */
void i2c_del_driver(struct i2c_driver *driver)
{
    i2c_for_each_dev(driver, process_removed_driver_ext);

    driver_unregister(&driver->driver);
    pr_debug("driver [%s] unregistered\n", driver->driver.name);
}
EXPORT_SYMBOL(i2c_del_driver);

/* ------------------------------------------------------------------------- */

struct i2c_addr_cnt {
    int addr;
    int cnt;
};

static int i2c_check_addr_ext(struct device *dev, void *addrp)
{
    struct i2c_client *client = i2c_verify_client(dev);
    struct i2c_addr_cnt *addrinfo = (struct i2c_addr_cnt *)addrp;
    int addr = addrinfo->addr;

    if (client && client->addr == addr) {
        addrinfo->cnt++;
    }

    return 0;
}

static int i2c_check_addr_ex(struct i2c_adapter *adapter, int addr)
{
    struct i2c_addr_cnt addrinfo;

    addrinfo.addr = addr;
    addrinfo.cnt = 0;
    device_for_each_child(&adapter->dev, &addrinfo, i2c_check_addr_ext);
    return addrinfo.cnt;
}

struct i2c_cmd_arg {
    unsigned cmd;
    void *arg;
};

static int i2c_cmd(struct device *dev, void *_arg)
{
    struct i2c_client *client = i2c_verify_client(dev);
    struct i2c_cmd_arg *arg = _arg;
    struct i2c_driver *driver;

    if (!client || !client->dev.driver) {
        return 0;
    }

    driver = to_i2c_driver(client->dev.driver);
    if (driver->command) {
        driver->command(client, arg->cmd, arg->arg);
    }
    return 0;
}

void i2c_clients_command(struct i2c_adapter *adap, unsigned int cmd, void *arg)
{
    struct i2c_cmd_arg cmd_arg;

    cmd_arg.cmd = cmd;
    cmd_arg.arg = arg;
    device_for_each_child(&adap->dev, &cmd_arg, i2c_cmd);
}
EXPORT_SYMBOL(i2c_clients_command);

static int __init i2c_init(void)
{
    int retval;

    retval = of_alias_get_highest_id("i2c");

    down_write(&__i2c_board_lock);
    if (retval >= __i2c_first_dynamic_bus_num) {
        __i2c_first_dynamic_bus_num = retval + 1;
    }
    up_write(&__i2c_board_lock);

    retval = bus_register(&i2c_bus_type);
    if (retval) {
        return retval;
    }

    is_registered = true;

#ifdef CONFIG_I2C_COMPAT
    i2c_adapter_compat_class = class_compat_register("i2c-adapter");
    if (!i2c_adapter_compat_class) {
        retval = -ENOMEM;
        goto bus_err;
    }
#endif
    retval = i2c_add_driver(&dummy_driver);
    if (retval) {
        goto class_err;
    }

    if (IS_ENABLED(CONFIG_OF_DYNAMIC)) {
        WARN_ON(of_reconfig_notifier_register(&i2c_of_notifier));
    }
    if (IS_ENABLED(CONFIG_ACPI)) {
        WARN_ON(acpi_reconfig_notifier_register(&i2c_acpi_notifier));
    }

    return 0;

class_err:
#ifdef CONFIG_I2C_COMPAT
    class_compat_unregister(i2c_adapter_compat_class);
bus_err:
#endif
    is_registered = false;
    bus_unregister(&i2c_bus_type);
    return retval;
}

static void __exit i2c_exit(void)
{
    if (IS_ENABLED(CONFIG_ACPI)) {
        WARN_ON(acpi_reconfig_notifier_unregister(&i2c_acpi_notifier));
    }
    if (IS_ENABLED(CONFIG_OF_DYNAMIC)) {
        WARN_ON(of_reconfig_notifier_unregister(&i2c_of_notifier));
    }
    i2c_del_driver(&dummy_driver);
#ifdef CONFIG_I2C_COMPAT
    class_compat_unregister(i2c_adapter_compat_class);
#endif
    bus_unregister(&i2c_bus_type);
    tracepoint_synchronize_unregister();
}

/* We must initialize early, because some subsystems register i2c drivers
 * in subsys_initcall() code, but are linked (and initialized) before i2c.
 */
postcore_initcall(i2c_init);
module_exit(i2c_exit);

/* ----------------------------------------------------
 * the functional interface to the i2c busses.
 * ----------------------------------------------------
 */

/* Check if val is exceeding the quirk IFF quirk is non 0 */
#define i2c_quirk_exceeded(val, quirk) ((quirk) && ((val) > (quirk)))

static int i2c_quirk_error(struct i2c_adapter *adap, struct i2c_msg *msg, char *err_msg)
{
    dev_err_ratelimited(&adap->dev, "adapter quirk: %s (addr 0x%04x, size %u, %s)\n", err_msg, msg->addr, msg->len,
                        msg->flags & I2C_M_RD ? "read" : "write");
    return -EOPNOTSUPP;
}

#define I2C_CHECK_MAX_NUM 2
static int i2c_check_for_quirks(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
{
    const struct i2c_adapter_quirks *q = adap->quirks;
    int max_num = q->max_num_msgs, i;
    bool do_len_check = true;

    if (q->flags & I2C_AQ_COMB) {
        max_num = I2C_CHECK_MAX_NUM;

        /* special checks for combined messages */
        if (num == I2C_CHECK_MAX_NUM) {
            if ((q->flags & I2C_AQ_COMB_WRITE_FIRST) && (msgs[0].flags & I2C_M_RD)) {
                return i2c_quirk_error(adap, &msgs[0], "1st comb msg must be write");
            }

            if ((q->flags & I2C_AQ_COMB_READ_SECOND) && !(msgs[1].flags & I2C_M_RD)) {
                return i2c_quirk_error(adap, &msgs[1], "2nd comb msg must be read");
            }

            if ((q->flags & I2C_AQ_COMB_SAME_ADDR) && (msgs[0].addr != msgs[1].addr)) {
                return i2c_quirk_error(adap, &msgs[0], "comb msg only to same addr");
            }

            if (i2c_quirk_exceeded(msgs[0].len, q->max_comb_1st_msg_len)) {
                return i2c_quirk_error(adap, &msgs[0], "msg too long");
            }

            if (i2c_quirk_exceeded(msgs[1].len, q->max_comb_2nd_msg_len)) {
                return i2c_quirk_error(adap, &msgs[1], "msg too long");
            }

            do_len_check = false;
        }
    }

    if (i2c_quirk_exceeded(num, max_num)) {
        return i2c_quirk_error(adap, &msgs[0], "too many messages");
    }

    for (i = 0; i < num; i++) {
        u16 len = msgs[i].len;

        if (msgs[i].flags & I2C_M_RD) {
            if (do_len_check && i2c_quirk_exceeded(len, q->max_read_len)) {
                return i2c_quirk_error(adap, &msgs[i], "msg too long");
            }

            if ((q->flags & I2C_AQ_NO_ZERO_LEN_READ) && len == 0) {
                return i2c_quirk_error(adap, &msgs[i], "no zero length");
            }
        } else {
            if (do_len_check && i2c_quirk_exceeded(len, q->max_write_len)) {
                return i2c_quirk_error(adap, &msgs[i], "msg too long");
            }

            if ((q->flags & I2C_AQ_NO_ZERO_LEN_WRITE) && len == 0) {
                return i2c_quirk_error(adap, &msgs[i], "no zero length");
            }
        }
    }

    return 0;
}

/**
 * __i2c_transfer - unlocked flavor of i2c_transfer
 * @adap: Handle to I2C bus
 * @msgs: One or more messages to execute before STOP is issued to
 *    terminate the operation; each message begins with a START.
 * @num: Number of messages to be executed.
 *
 * Returns negative errno, else the number of messages executed.
 *
 * Adapter lock must be held when calling this function. No debug logging
 * takes place. adap->algo->master_xfer existence isn't checked.
 */
int __i2c_transfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
{
    unsigned long orig_jiffies;
    int ret, try;

    if (WARN_ON(!msgs || num < 1)) {
        return -EINVAL;
    }

    ret = __i2c_check_suspended(adap);
    if (ret) {
        return ret;
    }

    if (adap->quirks && i2c_check_for_quirks(adap, msgs, num)) {
        return -EOPNOTSUPP;
    }

    /*
     * i2c_trace_msg_key gets enabled when tracepoint i2c_transfer gets
     * enabled.  This is an efficient way of keeping the for-loop from
     * being executed when not needed.
     */
    if (static_branch_unlikely(&i2c_trace_msg_key)) {
        int i;
        for (i = 0; i < num; i++) {
            if (msgs[i].flags & I2C_M_RD) {
                trace_i2c_read(adap, &msgs[i], i);
            } else {
                trace_i2c_write(adap, &msgs[i], i);
            }
        }
    }

    /* Retry automatically on arbitration loss */
    orig_jiffies = jiffies;
    for (ret = 0, try = 0; try <= adap->retries; try++) {
        if (i2c_in_atomic_xfer_mode() && adap->algo->master_xfer_atomic) {
            ret = adap->algo->master_xfer_atomic(adap, msgs, num);
        } else {
            ret = adap->algo->master_xfer(adap, msgs, num);
        }

        if (ret != -EAGAIN) {
            break;
        }
        if (time_after(jiffies, orig_jiffies + adap->timeout)) {
            break;
        }
    }

    if (static_branch_unlikely(&i2c_trace_msg_key)) {
        int i;
        for (i = 0; i < ret; i++) {
            if (msgs[i].flags & I2C_M_RD) {
                trace_i2c_reply(adap, &msgs[i], i);
            }
        }
        trace_i2c_result(adap, num, ret);
    }

    return ret;
}
EXPORT_SYMBOL(__i2c_transfer);

/**
 * i2c_transfer - execute a single or combined I2C message
 * @adap: Handle to I2C bus
 * @msgs: One or more messages to execute before STOP is issued to
 *    terminate the operation; each message begins with a START.
 * @num: Number of messages to be executed.
 *
 * Returns negative errno, else the number of messages executed.
 *
 * Note that there is no requirement that each message be sent to
 * the same slave address, although that is the most common model.
 */
int i2c_transfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
{
    int ret;

    if (!adap->algo->master_xfer) {
        dev_dbg(&adap->dev, "I2C level transfers not supported\n");
        return -EOPNOTSUPP;
    }

    /* REVISIT the fault reporting model here is weak:
     *
     *  - When we get an error after receiving N bytes from a slave,
     *    there is no way to report "N".
     *
     *  - When we get a NAK after transmitting N bytes to a slave,
     *    there is no way to report "N" ... or to let the master
     *    continue executing the rest of this combined message, if
     *    that's the appropriate response.
     *
     *  - When for example "num" is two and we successfully complete
     *    the first message but get an error part way through the
     *    second, it's unclear whether that should be reported as
     *    one (discarding status on the second message) or errno
     *    (discarding status on the first one).
     */
    ret = __i2c_lock_bus_helper(adap);
    if (ret) {
        return ret;
    }

    ret = __i2c_transfer(adap, msgs, num);
    i2c_unlock_bus(adap, I2C_LOCK_SEGMENT);

    return ret;
}
EXPORT_SYMBOL(i2c_transfer);

/**
 * i2c_transfer_buffer_flags - issue a single I2C message transferring data
 *                   to/from a buffer
 * @client: Handle to slave device
 * @buf: Where the data is stored
 * @count: How many bytes to transfer, must be less than 64k since msg.len is u16
 * @flags: The flags to be used for the message, e.g. I2C_M_RD for reads
 *
 * Returns negative errno, or else the number of bytes transferred.
 */
int i2c_transfer_buffer_flags(const struct i2c_client *client, char *buf, int count, u16 flags)
{
    int ret;
    struct i2c_msg msg = {
        .addr = client->addr,
        .flags = flags | (client->flags & I2C_M_TEN),
        .len = count,
        .buf = buf,
    };

    ret = i2c_transfer(client->adapter, &msg, 1);

    /*
     * If everything went ok (i.e. 1 msg transferred), return #bytes
     * transferred, else error code.
     */
    return (ret == 1) ? count : ret;
}
EXPORT_SYMBOL(i2c_transfer_buffer_flags);

/**
 * i2c_get_device_id - get manufacturer, part id and die revision of a device
 * @client: The device to query
 * @id: The queried information
 *
 * Returns negative errno on error, zero on success.
 */
#define I2C_GET_ID_BLOCK0_VALUE 3
#define I2C_GET_ID_BLOCK0_REG 0
#define I2C_GET_ID_BLOCK1_REG 1
#define I2C_GET_ID_BLOCK2_REG 2
#define I2C_GET_ID_BLOCK3_REG 3
#define I2C_GET_ID_SHIFT_TRHEE_MASK 3
#define I2C_GET_ID_SHIFT_FOUR_MASK 4
#define I2C_GET_ID_SHIFT_FIVE_MASK 5
#define I2C_LOW_FOUE_BYTE_BIT_MASK 0xf
#define I2C_LOW_TRHEE_BYTE_BIT_MASK 0x7

int i2c_get_device_id(const struct i2c_client *client, struct i2c_device_identity *id)
{
    struct i2c_adapter *adap = client->adapter;
    union i2c_smbus_data raw_id;
    int ret;

    if (!i2c_check_functionality(adap, I2C_FUNC_SMBUS_READ_I2C_BLOCK)) {
        return -EOPNOTSUPP;
    }

    raw_id.block[I2C_GET_ID_BLOCK0_REG] = I2C_GET_ID_BLOCK0_VALUE;
    ret = i2c_smbus_xfer(adap, I2C_ADDR_DEVICE_ID, 0, I2C_SMBUS_READ, client->addr << 1, I2C_SMBUS_I2C_BLOCK_DATA,
                         &raw_id);
    if (ret) {
        return ret;
    }

    id->manufacturer_id = (raw_id.block[I2C_GET_ID_BLOCK1_REG] << I2C_GET_ID_SHIFT_FOUR_MASK) |
                          (raw_id.block[I2C_GET_ID_BLOCK2_REG] >> I2C_GET_ID_SHIFT_FOUR_MASK);
    id->part_id = ((raw_id.block[I2C_GET_ID_BLOCK2_REG] & I2C_LOW_FOUE_BYTE_BIT_MASK) << I2C_GET_ID_SHIFT_FIVE_MASK) |
                  (raw_id.block[I2C_GET_ID_BLOCK3_REG] >> I2C_GET_ID_SHIFT_TRHEE_MASK);
    id->die_revision = raw_id.block[I2C_GET_ID_BLOCK3_REG] & I2C_LOW_TRHEE_BYTE_BIT_MASK;
    return 0;
}
EXPORT_SYMBOL_GPL(i2c_get_device_id);

/* ----------------------------------------------------
 * the i2c address scanning function
 * Will not work for 10-bit addresses!
 * ----------------------------------------------------
 */

/*
 * Legacy default probe function, mostly relevant for SMBus. The default
 * probe method is a quick write, but it is known to corrupt the 24RF08
 * EEPROMs due to a state machine bug, and could also irreversibly
 * write-protect some EEPROMs, so for address ranges 0x30-0x37 and 0x50-0x5f,
 * we use a short byte read instead. Also, some bus drivers don't implement
 * quick write, so we fallback to a byte read in that case too.
 * On x86, there is another special case for FSC hardware monitoring chips,
 * which want regular byte reads (address 0x73.) Fortunately, these are the
 * only known chips using this I2C address on PC hardware.
 * Returns 1 if probe succeeded, 0 if not.
 */
#define I2C_X86_ADDR_DEFAULT_VALUE 0x73
#define I2C_ADDR_LOW_THREE_BYTE_BIT_MASK 0x07
#define I2C_ADDR_LOW_FOUR_BYTE_BIT_MASK 0x0f
#define I2C_ADDR_DEFAULT_VALUE_ONE 0x30
#define I2C_ADDR_DEFAULT_VALUE_TWO 0x50
static int i2c_default_probe(struct i2c_adapter *adap, unsigned short addr)
{
    int err;
    union i2c_smbus_data dummy;

#ifdef CONFIG_X86
    if (addr == I2C_X86_ADDR_DEFAULT_VALUE && (adap->class & I2C_CLASS_HWMON) &&
        i2c_check_functionality(adap, I2C_FUNC_SMBUS_READ_BYTE_DATA)) {
        err = i2c_smbus_xfer(adap, addr, 0, I2C_SMBUS_READ, 0, I2C_SMBUS_BYTE_DATA, &dummy);
    } else
#endif
        if (!((addr & ~I2C_ADDR_LOW_THREE_BYTE_BIT_MASK) == I2C_ADDR_DEFAULT_VALUE_ONE ||
              (addr & ~I2C_ADDR_LOW_FOUR_BYTE_BIT_MASK) == I2C_ADDR_DEFAULT_VALUE_TWO) &&
            i2c_check_functionality(adap, I2C_FUNC_SMBUS_QUICK)) {
                err = i2c_smbus_xfer(adap, addr, 0, I2C_SMBUS_WRITE, 0, I2C_SMBUS_QUICK, NULL);
    } else if (i2c_check_functionality(adap, I2C_FUNC_SMBUS_READ_BYTE)) {
        err = i2c_smbus_xfer(adap, addr, 0, I2C_SMBUS_READ, 0, I2C_SMBUS_BYTE, &dummy);
    } else {
        dev_warn(&adap->dev, "No suitable probing method supported for address 0x%02X\n", addr);
        err = -EOPNOTSUPP;
    }

    return err >= 0;
}

static int i2c_detect_address(struct i2c_client *temp_client, struct i2c_driver *driver)
{
    struct i2c_board_info info;
    struct i2c_adapter *adapter = temp_client->adapter;
    int addr = temp_client->addr;
    int err;

    /* Make sure the address is valid */
    err = i2c_check_7bit_addr_validity_strict(addr);
    if (err) {
        dev_warn(&adapter->dev, "Invalid probe address 0x%02x\n", addr);
        return err;
    }

    /* Skip if already in use (7 bit, no need to encode flags) */
    if (i2c_check_addr_busy(adapter, addr)) {
        return 0;
    }

    /* Make sure there is something at this address */
    if (!i2c_default_probe(adapter, addr)) {
        return 0;
    }

    /* Finally call the custom detection function */
    memset(&info, 0, sizeof(struct i2c_board_info));
    info.addr = addr;
    err = driver->detect(temp_client, &info);
    if (err) {
        /* -ENODEV is returned if the detection fails. We catch it
           here as this isn't an error. */
        return err == -ENODEV ? 0 : err;
    }

    /* Consistency check */
    if (info.type[0] == '\0') {
        dev_err(&adapter->dev, "%s detection function provided no name for 0x%x\n", driver->driver.name, addr);
    } else {
        struct i2c_client *client;

        /* Detection succeeded, instantiate the device */
        if (adapter->class & I2C_CLASS_DEPRECATED) {
            dev_warn(&adapter->dev,
                     "This adapter will soon drop class based instantiation of devices. "
                     "Please make sure client 0x%02x gets instantiated by other means. "
                     "Check 'Documentation/i2c/instantiating-devices.rst' for details.\n",
                     info.addr);
        }

        dev_dbg(&adapter->dev, "Creating %s at 0x%02x\n", info.type, info.addr);
        client = i2c_new_client_device(adapter, &info);
        if (!IS_ERR(client)) {
            list_add_tail(&client->detected, &driver->clients);
        } else {
            dev_err(&adapter->dev, "Failed creating %s at 0x%02x\n", info.type, info.addr);
        }
    }
    return 0;
}

static int i2c_detect(struct i2c_adapter *adapter, struct i2c_driver *driver)
{
    const unsigned short *address_list;
    struct i2c_client *temp_client;
    int i, err = 0;

    address_list = driver->address_list;
    if (!driver->detect || !address_list) {
        return 0;
    }

    /* Warn that the adapter lost class based instantiation */
    if (adapter->class == I2C_CLASS_DEPRECATED) {
        dev_dbg(&adapter->dev,
                "This adapter dropped support for I2C classes and won't auto-detect %s devices anymore. "
                "If you need it, check 'Documentation/i2c/instantiating-devices.rst' for alternatives.\n",
                driver->driver.name);
        return 0;
    }

    /* Stop here if the classes do not match */
    if (!(adapter->class & driver->class)) {
        return 0;
    }

    /* Set up a temporary client to help detect callback */
    temp_client = kzalloc(sizeof(struct i2c_client), GFP_KERNEL);
    if (!temp_client) {
        return -ENOMEM;
    }
    temp_client->adapter = adapter;

    for (i = 0; address_list[i] != I2C_CLIENT_END; i += 1) {
        dev_dbg(&adapter->dev, "found normal entry for adapter %d, addr 0x%02x\n", i2c_adapter_id(adapter),
                address_list[i]);
        temp_client->addr = address_list[i];
        err = i2c_detect_address(temp_client, driver);
        if (unlikely(err)) {
            break;
        }
    }

    kfree(temp_client);
    return err;
}

int i2c_probe_func_quick_read(struct i2c_adapter *adap, unsigned short addr)
{
    return i2c_smbus_xfer(adap, addr, 0, I2C_SMBUS_READ, 0, I2C_SMBUS_QUICK, NULL) >= 0;
}
EXPORT_SYMBOL_GPL(i2c_probe_func_quick_read);

struct i2c_client *i2c_new_scanned_device(struct i2c_adapter *adap, struct i2c_board_info *info,
                                          unsigned short const *addr_list,
                                          int (*probe)(struct i2c_adapter *adap, unsigned short addr))
{
    int i;

    if (!probe) {
        probe = i2c_default_probe;
    }

    for (i = 0; addr_list[i] != I2C_CLIENT_END; i++) {
        /* Check address validity */
        if (i2c_check_7bit_addr_validity_strict(addr_list[i]) < 0) {
            dev_warn(&adap->dev, "Invalid 7-bit address 0x%02x\n", addr_list[i]);
            continue;
        }

        /* Check address availability (7 bit, no need to encode flags) */
        if (i2c_check_addr_busy(adap, addr_list[i])) {
            dev_dbg(&adap->dev, "Address 0x%02x already in use, not probing\n", addr_list[i]);
            continue;
        }

        /* Test address responsiveness */
        if (probe(adap, addr_list[i])) {
            break;
        }
    }

    if (addr_list[i] == I2C_CLIENT_END) {
        dev_dbg(&adap->dev, "Probing failed, no device found\n");
        return ERR_PTR(-ENODEV);
    }

    info->addr = addr_list[i];
    return i2c_new_client_device(adap, info);
}
EXPORT_SYMBOL_GPL(i2c_new_scanned_device);

struct i2c_adapter *i2c_get_adapter(int nr)
{
    struct i2c_adapter *adapter;

    mutex_lock(&core_lock);
    adapter = idr_find(&i2c_adapter_idr, nr);
    if (!adapter) {
        goto exit;
    }

    if (try_module_get(adapter->owner)) {
        get_device(&adapter->dev);
    } else {
        adapter = NULL;
    }

exit:
    mutex_unlock(&core_lock);
    return adapter;
}
EXPORT_SYMBOL(i2c_get_adapter);

void i2c_put_adapter(struct i2c_adapter *adap)
{
    if (!adap) {
        return;
    }

    put_device(&adap->dev);
    module_put(adap->owner);
}
EXPORT_SYMBOL(i2c_put_adapter);

/**
 * i2c_get_dma_safe_msg_buf() - get a DMA safe buffer for the given i2c_msg
 * @msg: the message to be checked
 * @threshold: the minimum number of bytes for which using DMA makes sense.
 *           Should at least be 1.
 *
 * Return: NULL if a DMA safe buffer was not obtained. Use msg->buf with PIO.
 *       Or a valid pointer to be used with DMA. After use, release it by
 *       calling i2c_put_dma_safe_msg_buf().
 *
 * This function must only be called from process context!
 */
u8 *i2c_get_dma_safe_msg_buf(struct i2c_msg *msg, unsigned int threshold)
{
    /* also skip 0-length msgs for bogus thresholds of 0 */
    if (!threshold) {
        pr_debug("DMA buffer for addr=0x%02x with length 0 is bogus\n", msg->addr);
    }
    if (msg->len < threshold || msg->len == 0) {
        return NULL;
    }

    if (msg->flags & I2C_M_DMA_SAFE) {
        return msg->buf;
    }

    pr_debug("using bounce buffer for addr=0x%02x, len=%d\n", msg->addr, msg->len);

    if (msg->flags & I2C_M_RD) {
        return kzalloc(msg->len, GFP_KERNEL);
    } else {
        return kmemdup(msg->buf, msg->len, GFP_KERNEL);
    }
}
EXPORT_SYMBOL_GPL(i2c_get_dma_safe_msg_buf);

/**
 * i2c_put_dma_safe_msg_buf - release DMA safe buffer and sync with i2c_msg
 * @buf: the buffer obtained from i2c_get_dma_safe_msg_buf(). May be NULL.
 * @msg: the message which the buffer corresponds to
 * @xferred: bool saying if the message was transferred
 */
void i2c_put_dma_safe_msg_buf(u8 *buf, struct i2c_msg *msg, bool xferred)
{
    if (!buf || buf == msg->buf) {
        return;
    }

    if (xferred && (msg->flags & I2C_M_RD)) {
        memcpy(msg->buf, buf, msg->len);
    }

    kfree(buf);
}
EXPORT_SYMBOL_GPL(i2c_put_dma_safe_msg_buf);

MODULE_AUTHOR("Simon G. Vogl <simon@tk.uni-linz.ac.at>");
MODULE_DESCRIPTION("I2C-Bus main module");
MODULE_LICENSE("GPL");
